In the 'Horus Heresy' series, Horus Lupercal is a central character. He was once a great and noble Primarch who ultimately turned to Chaos. Another important character is Roboute Guilliman, the Primarch of the Ultramarines. He is known for his strategic genius and his efforts to preserve the Imperium.
In the 'Gotrek & Felix' series, as the name suggests, Gotrek Gurnisson, the Dwarf Slayer, and Felix Jaeger, the human scribe, are the main characters. Gotrek is on a quest for a heroic death, and Felix follows him through all kinds of dangerous adventures, facing monsters and villains in the Warhammer Fantasy world.
In 'Gaunt's Ghosts', the main character is Colonel - Commissar Ibram Gaunt. He's a complex leader who has to balance military strategy with the Imperium's strict ideology.
I'm not sure specifically as I haven't read this graphic novel. But it could be Space Marines. They are often central in Warhammer 40K stories related to big events like Exterminatus.
There are likely to be Space Marines as main characters. They are often the heroes in the Warhammer stories, fighting against the forces of chaos.
One of the main characters is Sevatar. He is a central figure in the Night Lords legion and plays a significant role in their actions and politics.
In 'Malus Darkblade', the central character is Malus himself. He is a complex character, a dark elf with his own ambitions and desires. He has to face many challenges, both internal and external, as he tries to achieve his goals in the dangerous world of the Warhammer Fantasy.
The main character is likely Stormhammer. He could be a human with extraordinary abilities. Alongside him, there might be a mentor figure, someone who has trained him in the ways of war and magic. There may be a love interest as well, a female character who gives him emotional support and might also be involved in the battles in some way. And then there are the villains. Maybe a group of dark knights who have sworn allegiance to the forces of evil and are constantly hunting Stormhammer. Each of these characters would play a role in the complex plot of the novel, driving the story forward through their actions, decisions, and relationships.
I don't know for sure, but it could be the Space Marines. They are often central characters in Warhammer 40k stories.
In the Sigmar story, Sigmar himself is the main character. He's a strong - willed and fearless leader. His companions like Alaric the Mad also play important roles. They fight alongside Sigmar against the forces of chaos.
Nagash is a central figure in many of the novels related to necromancy and the undead. He is extremely powerful and his actions drive a lot of the dark magic - related plotlines. There are also characters like Karl Franz, the Emperor of the Empire, who has to deal with threats from all sides, be it Chaos invasions or Greenskin raids. He is a symbol of leadership and order in the Warhammer Fantasy world.
Often, soldiers are main characters. They are the ones facing the terrors on the front lines. They might be ordinary soldiers or elite warriors. For instance, a grizzled veteran who has seen many battles but is now confronted with a horror he can't explain.